DP, shading, NPR, Just N of NNTB - 333° DP, shading, NPR, Just N of NNTB - 343°
Fig. 3.1. A full disk drawing of Jupiter showing the shading or veil in the north polar region of Jupiter on October 26, 1997 (Credit: John W. McAnally).
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faint. A dusky patch or mottling is seen by me for the first time at the southern edge of the NPR (these had previously [recently] been reported by others). This mottling was very distinct and unmistakable! It was fairly extended in longitude. It was seen clearly enough that I was able to make a CM transit timing of the preceding and following edge. This may be the first measurement (CM transit timing of such a feature, at least during this apparition) reported to A.L.P.O. (this observation was made in integrated light). The mottling was also seen in green (W56) light. Not seen in yellow (W12) light." Alas, the feature disappeared and was not observed again. However, their existence was confirmed beyond doubt when these dusky markings were captured in a few CCD images, coinciding with the longitudinal position observed by me and several other observers. These dusky markings were first seen visually and later also confirmed by CCD imaging. A fine example that visual observations are still of value.
Often, the polar-regions seem to spread their gray appearance all the way to the NTZ or the STZ. Occasionally, however, subtle, lighter zones can be made out, divided by thin, grayish belts barely seen. Observing the often too subtle NNNTB and NNTB, their southern counterparts, and intervening zones, is extremely difficult. Consequently it is very difficult to collect current, useful data on the drift rates and wind currents in these regions. Occasions have been rare in which any useful transit timings have been obtained from the polarregions. However, when bright or dark features present themselves in these belts and zones for long enough, the observations that can be obtained are of great importance. As recent as July 2006, CCD and webcam images continued to reveal a north polar region that was mostly unremarkable (Figs. 3.2 and 3.3). However, the improved camera technology consistently revealed light and dark dusky markings in the region. With advances in CCD and webcam technology, we can expect amateurs to obtain images with such high resolution that features in the polar regions will be captured consistently with enough resolution that measurements of currents and drift rates in this region will not only become possible but routine.
Fig. 3.3. A webcam image showing a little more activity in Jupiter's north polar region, although the region is still unremarkable, on April 1 2, 2006. South is to the top right of image. (Credit: Donald C. Parker).
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